When a device uses services provided by a content provider, the device and a server belonging to the content provider perform mutual authentication. If the mutual authentication succeeds, the device and the server share a key, and thereby establish a so-called SAC (Secure Authentication Channel), which is a secure data transmission channel. The device and the server transmit and receive contents to and from each other via the SAC. Such a technique is disclosed by Patent Document 1.
In recent years, the number of content service providers has been increasing. Therefore, there are demands for a system that supports the case where a single device uses services provided by a plurality of content providers.
Patent Document 1: Japanese Laid-open Patent Document No. 11-234259;
Non-patent Document 1: “Gendai Ango Riron (Modern Encryption Theory)” written by Shinichi Ikeno and Kenji Koyama, and published by the Institute of Electronics and Communication Engineer.